The direction of light output from headlamps on motor vehicles requires proper aiming, both vertically and horizontally, for safe and optimal performance. Accordingly, adjustment or “aiming” is performed before a vehicle is put into service and may be performed from time to time thereafter if vibration or other conditions or events move the headlamp away from optimal positioning. It is known to provide headlamp assemblies adjustable about both vertical and horizontal axes with adjusters operated by screwdrivers or other implements for lengthening and shortening the adjuster to cause the headlamp assembly to pivot about an axis. Some known adjustment mechanisms include bushings, bosses, O-rings and push nuts that need to be connected to a screw during installation. Although adjusters of this type have proven to be useful, because of the many individual components required, labor for assembly and installation are high. It is preferable to have a pre-assembled adjuster that can be installed quickly and easily in the headlamp assembly and be ready for immediate adjustment.
In some known adjuster configurations, an output shaft is operatively connected to a movable reflector in the headlamp assembly. Linear movement of the adjuster output shaft pivots the reflector to change the direction of light reflected therefrom. In the adjuster, one or several gears can be driven by screwdrivers or other implements for rotating mechanisms in the adjuster and causing linear movement of the output shaft. Problems and difficulties can be encountered if the adjuster is adjusted too far in either direction. If moved axially longer than intended, the headlamp assembly or the adjuster can be damaged, requiring repair or replacement. If withdrawn too far, the output shaft can become disengaged from its driving mechanisms, again causing difficulties and problems which may require replacement or disassembly and repair. When such over adjustment occurs on an assembly line, assembly line output is adversely affected. If over adjustment occurs after the vehicle has been placed in use, access for repairing or replacing the adjustment mechanism can require significant disassembly and cost in time and expense. Placing axial restraints on the movement of the output shaft of the adjuster can eliminate the problem of over adjustment in either direction, but also may result in damage to the drive mechanisms of the adjuster if the restraints are encountered and adjustment attempts continue. Damage may be more likely if powered tools are used for effecting the adjustment.
What is needed is a headlamp adjusted that can tolerate over adjustment in either direction, without damage to the adjuster or to the headlamp assembly in which it is installed, and without becoming disengaged to the extent of being nonfunctional for all purposes.